CTD rosette

This image shows a rosette of Niskin (seawater sampling) bottles, on a frame with instruments for measuring depth, temperature, and density (salinity), as well as the MBARI-designed ISUS (In-situ Nitrate analyzer).

The CTD measures conductivity (which helps determine salinity), temperature, and depth. This particular CTD runs profiles of the water column (surface to bottom) and along the way, collects discrete water samples (at specific predetermined depths) using the rosette of niskin bottles. Each bottle can collect a water sample. The transmissometer measures the number of particles in the water and the oxygen sensors tell us how much dissolved oxygen is present. Both of these instruments go onto the CTD rosette and give us a profile of the water column.